In alignment and troubleshooting of circuits involving calibration of voltage or current pulse amplitudes, such as the beam current of a pulsed TWT, it is necessary to accurately monitor the amplitude of pulse transformers and display the waveforms on an oscilloscope.
There are several techniques for measuring pulse amplitudes. One method displays the pulse with or without a pulse transformer on an oscilloscope and measures its amplitude. This method is generally not very accurate, being limited by the oscilloscope accuracy of 2 to 3 percent unless expensive, differential comparator type input processing is utilized. In addition valuable time is being spent setting up the oscilloscope and human error is introduced in interpreting the display. Another prior method is the use of convention sample and hold circuits, in conjunction with a measuring device such as a digital panel meter. This method greatly increases accuracy but requires some type of accurate timing circuit to produce sample gates during the pulse whose amplitude is being determined. The circuit requires adjustments as to gain, voltage offset, as well as timing for the sample gate.
The present invention allows for a simple, inexpensive, continuous accurate monitoring of pulse amplitude by any high impedance measuring device (such as a digital panel meter), without resorting to display techniques such as an oscilloscope or transient analyzer. The device makes use of sample and hold techniques for storing amplitudes of pulse waveforms. The circuit which utlizes only one I.C. comparator and one FET generates a sample gate pulse without requiring additional circuitry for timing and sync pulse generation.
Sone of the advantages of the present invention are the following: inexpensive, calibration-free, ease of use so as not to require interpretation, high accuracy on the order of 0.001 percent, simplicity, and temperature insensitive.
The present invention may be utilized in TWT beam current monitoring. It may be used as a module to allow digital panel meters, VTVM, or DVM to read peak pulse amplitude. Further, it may be utilized in a photoflash intensity converter. Still further, it may be a simplified hold circuit for pulse amplitude A/D conversion. Finally, it may be used in accurate "0" and"1" voltage determination for TTL type logic using dynamic pulse rather than static DC level testing.